1. Field of the Invention
The present invention relates to photography, and more particularly to a control circuit and method for practicing time exposure photography.
2. Description of the Prior Art
Typical shutter speeds in a single lens reflex camera range from 1/8000 seconds to 30 seconds (the fastest shutter speed typically varying with type of camera). For time exposures of more than 30 seconds, typically requiring a manual mode of operation in a single lens reflex camera, the user switches to a B shutter photographing mode.
To photograph scenes under low ambient light conditions, time exposure photography is typically practiced without artificial light. To take a time exposure picture, the user sets the camera to the B (Bulb) shutter mode. The shutter button is depressed to open the shutter, and the shutter remains open to expose the film as long as the shutter button is held depressed. The film exposure time is concluded when the shutter button is released. Alternatively, the B shutter mode may be executed in some cameras by depressing and releasing the shutter button to open the shutter and then pressing and releasing the shutter button again to close the shutter.
However, the exposure time required to obtain a correctly exposed photograph depends on the user's experience with time exposure photography. Too short an exposure time, and the resulting picture is dark. Too long an exposure time, and the resulting picture is washed out. In neither case is the picture of an acceptable quality.
It is difficult, particularly for an inexperienced photographer, to obtain proper film exposure time using the B shutter mode, since it is left to the photographer to determine the proper exposure time. Also, having to manually actuate the shutter button to open and close the shutter is inconvenient and may cause camera motion that could spoil the picture.